BR102015015930B1 - hydrotreating catalyst with high molybdenum density, its preparation processes and hydrodesulfurization process of a gasoline cut - Google Patents

Abstract

HYDRO TREATMENT CATALYST WITH HIGH MOLIBDEN DENSITY AND PREPARATION METHOD. The present invention relates to a hydrotreating catalyst, comprising an alumina-based support, at least one metal in the VIB group, at least one metal in the VIII group and phosphorus in which: the specific surface of the catalyst is comprised between 20 and 150 m2 / g; the metal density of the VIB group, expressed as the number of metal atoms of the VIB group per unit surface of the catalyst, is between 7 and 30 metal atoms of the VIB group per nm2 of catalyst .; the catalyst being prepared by impregnating the metals of the VIB group, of the VIII group and of the phosphorus on the support, in order to obtain an impregnated catalytic precursor, after drying of this impregnated precursor at a temperature below 200 ° C and without subsequent calcination .

Description

[001] The present invention relates to a hydrotreating catalyst, and a process for preparing that catalyst useful for the hydrodesulfurization of an oil fraction, in particular a gasoline fraction.

[002] The invention also relates to a hydrodesulfurization process of a fraction of gasoline, using a catalyst, according to the invention.

TECHNICAL STATUS

[003] Oil refining, as well as petrochemicals, are then subjected to new problems. In effect, all countries are progressively adopting stringent sulfur specifications, the goal being to achieve 10 ppm (by weight) of sulfur in commercial gasolines in Europe and Japan. The problem of reducing sulfur content is essentially concentrated in gasolines obtained by cracking, whether catalytic (FCC Fluid Catalytic, according to Anglo-Saxon terminology) or non-catalytic (coking, visco-reduction, vapocraque), the main sulfur precursors in the gasoline pools.

[004] A solution, well known to the person skilled in the art to reduce the sulfur content is to perform a hydrotreating (or hydrodesulfurization) of the hydrocarbon fractions (and notably catalytic cracking gasolines) in the presence of hydrogen and a heterogeneous catalyst. However, this process has the major drawback of causing a very important drop in the octane index, if the catalyst used is not very selective. This decrease in the octane index is notably linked to the hydrogenation of the olefins present in this type of gasoline in a manner concomitant with hydrodesulfurization. Contrary to other hydrotreating processes, the hydrodesulphurisation of gasolines must therefore allow us to respond to a double antagonistic effort: to ensure a profound hydrodesulphurisation of gasolines and limit the hydrogenation of the unsaturated compounds present.

[005] Thus, US patent 5 318 690 proposes a process that consists of fractionating gasoline, moderating the light fraction and hydrotreating the heavy fraction over a conventional catalyst, then treating it over a ZSM5 zeolite to find approximately the index of initial octane.

[006] Patent application WO 01/40409 claims the treatment of FCC gasoline under conditions of high temperature, low pressure and high hydrogen / charge ratio. In these particular conditions, recombination reactions leading to the formation of mercaptan, putting into play the H2S formed by the desulfurization reaction and olefins are minimized.

[007] Finally, the US patent 5 968 346 proposes a scheme that allows to reach very low residual sulfur contents through a process in several stages; hydrodesulfurization on a first catalyst, separation of liquid and gaseous fractions, and second hydrotreatment on a second catalyst. The liquid / gas separation allows to eliminate the H2S formed in the first reactor, in order to reach a better compromise between hydrodesulfurization and octane loss.

[008] Another way to respond to the double problem mentioned above is to employ hydrodesulfurization catalysts that are active in hydrodesulfurization, but also very selective in hydrodesulfurization in relation to the olefin hydrogenation reaction.

[009] Thus, the document US 2009/321320 is known in the state of the art, which discloses hydrodesulfurization catalysts that comprise a metallic phase active in cobalt / molybdenum based on high temperature alumina, that is, calcined at a temperature above at 800 oC and a surface area between 40 and 200 m2 / g. The catalysts are obtained by dry impregnating an aqueous solution containing cobalt, molybdenum and at least one additive in the form of an organic compound.

[0010] EP 1892039 describes selective hydrodesulfurization catalysts comprising at least one support, at least one group VIII element, at least one element of the VIB group and phosphorus in which the density in elements of the VIB group per unit of support surface is between 2.10-4 and 18.10-4 g of oxides of elements of the VIB group per m2 of support, in which the molar ratio of phosphorus to element of the VIB group is between 0.27 and 2, in which the content of elements in the VIB group is between 1 and 20% by weight of oxides of elements in the VIB group and in which the substrate has a specific surface area of less than 135 m2 // g.

[0011] Fuel oil hydrotreating catalysts are also known, comprising a support, at least one metal of the VIB group associated with at least one metal of the group VIII, which have a specific surface comprised between 200 and 300 m2 / g, therefore, a density in metal of the VIB group per unit area, expressed in number of metal atoms of the VIB group per nm2 of catalyst, less than 7.

[0012] There is, therefore, still a keen interest today in the refiners for hydrodesulfurization catalysts, notably gasoline fractions that have improved catalytic performance, notably in terms of catalytic activity and, hydrodesulfurization and / or selectivity and that, once used, allow the production of gasoline with a low sulfur content without a severe reduction in the octane index.

SUMMARY OF THE INVENTION

[0013] The invention therefore relates to a hydrotreating catalyst comprising an alumina-based support, at least one metal in the VIB group, at least group VIII and the phosphorus on which: - the surface specific catalyst is between 20 and 150 m2 / g; - the metal density of the VIB group, expressed as the number of metal atoms of the VIB group per unit surface of the catalyst, is between 7 and 30 metal atoms of the VIB group per nm2 of catalyst; the catalyst being prepared by impregnating the metals of the VIB group, of the VIII group and of the phosphorus on the support, in order to obtain an impregnated catalytic precursor, after drying of this impregnated catalytic precursor at a temperature below 200 ° C and without subsequent calcination .

[0014] The metal content of the VIB group is generally between 3 and 35% by weight of the oxide of that metal in the VIB group in relation to the total weight of the catalyst.

[0015] The group VIII metal content is generally between 0.1 and 10% by weight of that group VIII metal oxide in relation to the total weight of the catalyst.

[0016] The phosphorus content is generally between 0.3 and 1% by weight of P2O5 in relation to the total weight of the cation to the total weight of the catalyst.

[0017] Preferably, the molar ratio (group VIII target) / (metal of the VIB group) is comprised between 0.1 and 0.8 and the phosphorus molar ratio (metal of the VIB group) is comprised between 0.1 and 0.7.

[0018] The catalyst, according to the invention, preferably has a specific surface area between 30 and 120 m2 / g, preferably between 40 and 95 m2 / g and most preferably between 50 and 90 m2 / g.

[0019] Preferably, the VIB group metal density is between 7 and 25 VIB group metal atoms per nm2 of catalyst, preferably between 7 and 20 VIB group metal atoms per nm2 of catalyst preferably between 7 and 15 metal atoms of the VIB group per nm2 of catalyst.

[0020] The metal in the VIB group is chosen from tungsten and molybdenum and the metal from group VIII is chosen from nickel and cobalt.

[0021] According to a preferred embodiment, the metal of the group VIB is molybdenum and the metal of group VIII is cobalt.

[0022] Within the scope of the invention, the alumina-based support of the catalyst is obtained from malaxed, shaped and calcined alumina gel.

[0023] According to the invention, the catalyst may further comprise at least one organic compound containing oxygen and / or nitrogen. The organic compound can be chosen from a carboxylic acid, an alcohol, an aldehyde, an ester, an amine, an amino carboxylic acid, an amino alcohol, a nitrile and an amide.

[0024] For example, the organic compound is chosen from ethylene, triethylene glycol, glycerol or polyethylene glycol having a molecular weight of 150 to 1500, acetophenone, 2,4-pentane dione, pentanol , acetic acid, maleic acid, oxalic acid, tartaric acid, formic acid, citric acid, a C1-C4 dialkyl succinate, a cyclic oligosaccharide composed of at least 6 glycopyran units linked in a (1-4), ethylene diamine, tetramethyl urea, triacetic amino acid, 1,2-cyclohexane diamine tetra acetic acid, mono-ethanol amine, acetonitrile, N-methyl pyrrolidone, dimethyl formamide and ethylene diamine tetraacetic acid

[0025] The invention also relates to a process for preparing the catalyst, according to the invention, which comprises the following steps: a) the metals of the group are deposited on an alumina-based support VIII, the VIB group and phosphorus in order to obtain an impregnated catalytic precursor; b) the impregnated precursor is dried at a temperature below 200 oC without subsequent calcination in order to provide a dried catalyst.

[0026] The catalyst, according to the invention, when it also comprises an organic additive, is prepared according to a process comprising the following steps: 1) it is deposited on an alumina-based support for a or various impregnations: metals of group VIII, group VIB, phosphorus and at least one organic compound containing oxygen and / or nitrogen in order to obtain an impregnated catalytic precursor; 11) the impregnated precursor is dried at a temperature below 200 oC without subsequent calcination, in order to provide a dried catalyst.

[0027] According to the invention, step (I) can comprise the following successive steps: 12) an alumina support is impregnated with at least one solution containing at least one metal of the VIB group, at least one metal group VIII and phosphorus to obtain an impregnated support; 13) the impregnated support obtained in step I1) is dried at a temperature below 200 oC without subsequent calcination to obtain a dried catalyst; 14) the dried catalyst obtained in step I2) is impregnated with an impregnation solution comprising at least one organic compound containing oxygen and / or nitrogen to obtain an additive catalyst precursor; 15) optionally, the additive catalyst precursor obtained in step (3) is allowed to mature.

[0028] Finally, the invention also has as its object a process of desulfurizing a fraction of gasoline in which that fraction of gasoline, hydrogen and a catalyst, in accordance with the invention or prepared, in accordance with one of the processes that sulfurized. Contact is made at: • a temperature between 200 and 400 oC; • a total pressure between 1 and 3 MPa; • an hourly volume velocity, defined as the volume flow of charge taken to the catalyst volume, between 1 and 10 h-1; • a hydrogen volume / gasoline ratio between 100 and 600 Nl / l.

[0029] Gasoline that is treated by the hydrodesulfurization process is preferably gasoline from a catalytic cracking unit. DETAILED DESCRIPTION OF THE INVENTION

[0030] The applicant thus discovered a hydrotreating catalyst, comprising a support based on alumina and metals in groups VIB and VIII of the periodic classification of elements and phosphorus which, after sulfurization, not only presents an improved hydrodesulphurization activity. , but also a high selectivity in hydro-desulfurization in relation to the hydrogenation reaction of olefins.

[0031] According to a first aspect, the invention relates to a hydrotreating catalyst comprising an alumina-based support, at least one group VIB metal, at least one group VIII and phosphorus metal, in which: • the specific surface of the catalyst is between 20 and 150 m2 / g; • the density of metal in the VIB group, expressed in the number of metal atoms in the VIB group per unit surface of the catalyst, is between 7 and 30 metal atoms in the VIB group per nm2 of catalyst; the catalyst being prepared by impregnating the metals of the VIB group, of the VIII group and of the phosphorus on the support in order to obtain an impregnated catalytic precursor, then by drying this impregnated catalytic precursor, then by drying that impregnated catalytic precursor. at a temperature below 200 oC and without subsequent calcination.

[0032] According to the invention, the density of metal in the VIB group, expressed as the number of metal atoms in the VIB group per unit surface of the catalyst (number of metal atoms in the VIB group per nm2 of catalyst) ) is calculated, for example, from the following ratio: d (metal in the VIB group) = (X x NA) / (100 x 1018 x SX MM) with: • X = weight% of metal in the VIB group; • NA = Avogadro's number equal to 6,022,1023; • S = Specific catalyst surface (m2 / g), measured according to ASTM D3663; • MM = molar mass of the metal in the VIB group (for example, 95.94 g / mol for molybdenum).

[0033] Surprisingly, the inventors established that a catalyst responding to the characteristics mentioned above is prepared by impregnating metals in the VIB and VIII group, and phosphorus, then only drying at a temperature below 200 oC, without suffering later a calcination step has a great activity in hydrodesulfurization, being more selective in face of the olefin hydrogenation reaction. The gain in activity makes it possible to reduce the reactor temperature to achieve the same rate of desulphurisation, with the benefit of limiting the deactivation phenomena, due, for example, to the coking of the catalyst and, therefore, keeping the unit in service for a additional duration compared to the performance obtained in the presence of state-of-the-art hydrodesulfurization catalysts (HDS). For example, the catalyst, according to the invention, shows a selectivity in hydrodesulfurization in relation to the hydrogenation of olefins that is improved, thus giving it an advantageous property in the context of hydrotreating fractions of gasoline-type hydrocarbons (is- that is, having a boiling temperature generally between 30 oC and 250 oC) containing olefins where it is sought to minimize the hydrogenation reaction of the olefins, in order to limit the loss of octane index of treated gasoline.

[0034] The catalyst, according to the invention, thus comprises a support on which an active metallic phase is deposited. The support is a porous solid based on alumina, that is, it contains aluminum and possibly metals and / or dopants that were introduced outside the metal impregnation stage of the active phase. For example, metals and / or dopants were introduced when preparing (malaxing, peptisation) of the support or when forming it.

[0035] Preferably, the support consists of alumina. Preferably, alumina is a delta, gamma or theta alumina, alone or in mixture.

[0036] The porous volume of the alumina support is generally between 0.4 cm3 / g and 1.3 cm3 / g, preferably between 0.6 cm3 / g. The total porous volume is measured by mercury porosimetry, according to ASTM D4284 with a humidity angle of 140o, as described in the work Rouquerol F .; Rouquerol J .; Singh K. ADsorption by Powders & Porous Solids: Principle, methodology and applications ", Academic Press, 1999, for example, by means of an Autporo IIITM model from Microméritics TM.

[0037] The specific surface of the alumina support is generally between 20 m2 / g and 200 m2 / g, preferably between 20 m2 / g and 180 m2 / g, more preferably between 30 m2 / g and 170 m2 // g. The specific surface is determined in the present invention by the method B.E.T., according to the standard ASTM D3663, method described in the same work mentioned above.

[0038] The alumina support is advantageously in the form of powder or in the form of spheres, extrudates, pellets, or irregular and non-spherical agglomerates, the specific shape of which may result from a stacking step.

[0039] According to a preferred embodiment, the catalyst, according to the invention, comprises an alumina support which is obtained from an alumina gel (or alumina gel) which essentially comprises a precursor of the oxy type (aluminum hydroxide (AlO (OH)) - also called bohemite. Alumina gel (or in other terms called bohemian gel) can be synthesized by precipitation of basic solutions and / or acids from aluminum salts induced by changing pH or any other method known to the person skilled in the art (P. Euzen, P. Raybaud, X. Krokidis, H. Toulhoat, JJ Le Loerer, JP Jolivet, C. FRoidefond, Alumina, inHandbook of Porous Soils, Eds F. Schuth, KSW Sing, J. Weitkamp, Wiley-VCH, Weinheim, Germany, 2002, pp. 1591-1677).

[0040] Generally, the precipitation reaction is carried out at a temperature between 5oC and 80oC and at a pH between 6 and 10. Preferably, the temperature is between 35oC and 70oC and the pH is between 6 and 10.

[0041] According to an embodiment, alumina gel is obtained by placing an aqueous solution of an acid aluminum salt in contact with a basic solution. For example, the acid aluminum salt is chosen from the group consisting of aluminum sulphate, aluminum nitrate or aluminum chloride. Preferably, that acidic salt is aluminum sulfate. The basic solution is preferably chosen from among soda or potash. Alternatively, an alkaline solution of aluminum salts can be put in contact, which can be chosen from the group consisting of sodium aluminate and potassium aluminate with an acid solution. In a most preferred variant, the gel is obtained by placing a solution of sodium aluminate in contact with nitric acid. The sodium alumina solution advantageously has a concentration between 10-5 and 10-1 mol.L-1 and, preferably, this concentration is between 10-4 and 10-2 mol.L- 1. According to another embodiment, alumina gel is obtained by contacting an aqueous solution of aluminum salts with an alkaline solution of aluminum salts. The alumina gel obtained after the precipitation step is then subjected to a kneading step, preferably in an acidic medium. The acid used can be, for example, nitric acid. This step is carried out by means of known instruments, such as Z-arm blenders, wheel blenders, mono or continuous screw allowing the transformation of the gel into a product that has the consistency of a paste.

[0042] According to an advantageous embodiment, one or more compounds called "porogen agents" are carried in the maxation medium. These compounds have the property to degrade by heating and thus create a porosity in the support. For example, wood flour, wood charcoal, tars, plastic materials can be used as porogen compounds.

[0043] The paste thus obtained, after kneading is, for example, passed through an extrusion die, when it is desired to obtain a support in the form of extruded. Generally, the extrudates have a diameter between 0.4 and 100 mm, preferably between 0.5 and 100 mm, more preferably between 0.5 and 10 mm and even more preferably between 0.4 and 100 mm. 4 mm. These extrudates can be cylindrical, multilobed (for example, trilobed or quadrilobed).

[0044] After forming, the support is eventually dried, before undergoing a heat treatment. For example, drying is carried out at a temperature between 100 and 200 oC.

[0045] The dried support then undergoes a heat treatment step that allows it to be given physical properties responding to the application under consideration.

[0046] According to a first embodiment, the heat treatment comprises at least one calcination step. The term "hypothermal treatment" means a treatment in the presence of water at a temperature above room temperature. Preferably, the hydrothermal treatment is carried out at a temperature between 100 and 300 oC, for 0.5 to 8 hours.

[0047] During this hydrothermal treatment, the alumina support can be treated in different ways. Thus, it is possible to previously impregnate the alumina in an acidic solution, then make it undergo a hydrothermal treatment either in the vapor phase or in the liquid phase. This impregnation, before hydrothermal treatment, can be carried out dry or by immersing the alumina in an acidic aqueous solution. Dry impregnation means putting the alumina in contact with a volume of solution less than or equal to the volume less than or equal to the volume of water taken up from the treated alumina. Preferably, the impregnation is carried out dry.

[0048] One can also treat the alumina support without prior impregnation with an acid solution, the acidity being in this case provided by an aqueous solution used, when the hydrothermal treatment itself.

[0049] The aqueous acidic solution comprises at least one acidic compound allowing to dissolve at least part of the alumina. The term "acidic compound properly dissolves at least part of the alumina, any acidic compound which, placed in contact with the alumina, performs the placing in solution of at least a part of the aluminum ions. The acid preferably allows , dissolve at least 0.5% by weight of alumina from the alumina support, preferably this acid is chosen from strong acids such as nitric acid, hydrochloric acid, perchloric acid, sulfuric acid or a weak acid, used at a concentration. Like its aqueous solution it has a pH below 4, as does acetic acid, or a mixture of these acids.

[0050] According to a preferred mode, hydrothermal treatment is carried out, in the presence of nitric acid and acetic acid considered alone or in mixture. This treatment can be carried out in an autoclave and, in this case, preferably in an autoclave with a rotating basket, as defined in patent application EP-A-0 387 109.

[0051] The hydrothermal treatment can also be carried out under saturating vapor pressure or under partial pressure of water vapor at least equal to 70% of the saturating vapor pressure corresponding to the treatment temperature.

[0052] The calcination step that occurs after the hydrothermal treatment, as this first embodiment takes place at a temperature generally between 400 and 1500 oC, preferably between 800 and 1300 oC, for 1 to 8 hours under air , whose water content is generally between 0 and 50% by weight.

[0053] According to a variant of the first embodiment of the heat treatment step, the dried support can also undergo successively a first calcination step, followed by a hydrothermal treatment step and, finally, a second calcination step . In this case, the two calcination steps are performed in the ranges of operating conditions described above, the operating conditions that can be identical or different in each of the calcination steps.

[0054] According to a second alternative embodiment of heat treatment, the support undergoes only a single heat treatment of calcination, that is, there is no hydrothermal treatment before or after this calcination. This is carried out at a temperature generally comprised between 400 and 1500 oC, preferably between 500 and 1200 oC, for 1 to 8 hours under air which has an eagle content generally comprised between 0 and 50% by weight. In this embodiment, the calcination step can be carried out in several steps with increasing temperature levels until reaching the desired final calcination temperature.

[0055] At the end of the final heat treatment, the substrate has a specific surface generally between 20 and 200 m2 / g. The support has a delta, gamma or theta alumina type crystallographic structure, alone or in mixture. The existence of the different crystallographic structures is linked notably to the conditions and use of heat treatment and, in particular, to the final calcination temperature.

[0056] The catalyst, according to the invention, is composed of an alumina support, phosphorus and an active phase formed of at least one metal of the group VIB and at least one metal of the group VIII. When prepared, the catalyst does not undergo calcination, that is, the impregnated catalytic precursor is not subjected to a heat treatment step at a temperature above 200 oC.

[0057] The total metal content of group VIII is comprised between 0.1 and 10% by weight of metal oxide of group VIII in relation to the total weight of the catalyst, preferably comprised between 0.6 and 8% in weight, preferably between 2 and 7%, most preferably between 2 and 6% by weight, and, even more preferably, between 3 and 6% by weight of metal oxide in the group VIII in relation to the total weight of the catalyst.

[0058] The metal content of the VIB group is between 3 and 35% by weight of the metal oxide of the VIB group in relation to the total weight of the catalysts, preferably between 5 and 30% by weight, preferably between 7 and 28% by weight, most preferably comprised between 10 and 25% by weight of the metal oxide of the VIB group in relation to the total weight of the catalyst.

[0059] The catalyst, according to the invention, has a phosphorus content generally comprised between 0.3 and 10% by weight of P2O5 in relation to the total weight of catalyst, preferably between 2 and 8% by weight of P2O5 in relative to the total weight of catalyst. For example, the phosphorus present in the catalyst is combined with the metal of the group VIB and possibly also with the metal of the group VIII in the form of heteropolyanions.

[0060] The hydrotreating catalyst according to the invention, in the form of oxide, is characterized by a specific surface area between 20 and 150 m2 / g, preferably between 30 and 120 m2 / g, preferably included between 40 and 95 m2 / g, most preferably between 50 and 90 m2 / g.

[0061] Furthermore, the catalyst has a metal density of the VIB group, expressed as the number of atoms of that metal per unit surface of the catalyst, which is comprised between 7 and 30 metal atoms of the VIB group per nm2 of catalyst , preferably comprised between 7 and 25 metal atoms of the VIB group of catalyst and most preferably comprised between 7 and 20 metal atoms of the VIB group per nm2 of catalyst. Even more preferably, the density of metal in the VIB group, expressed as the number of atoms of that metal per unit surface of the catalyst, is between 7 and 15 metal atoms in the VIB group per nm2 of catalyst. As an example, if the catalyst contains 20% by weight of molybdenum oxide MoO3 (ie 13.33% by weight of Mo) and has a specific surface of 100 m2 / g, the density d (Mo) is equal to: d (Mo) = (13.33 x NA) / (100 x1018 x 100 x 96) = 8.3 Mo atoms / nm2 of catalyst.

[0062] The molar ratio of metal of group VIII to metal of the catalyst group VIB is generally between 0.1 and 0.8, preferably between 0.2 and 0.6.

[0063] On the other hand, the phosphorus / molar ratio (metal of the VIB group) is generally between 0.1 and 0.7, preferably between 0.2 and 0.6.

[0064] The metal of the VIB group present in the active phase of the catalyst is preferably chosen from molybdenum and tungsten.

[0065] The group VIII metal present in the active phase of the catalyst is preferably chosen from cobalt, nickel and the mixture of these two elements.

[0066] The active phase of the catalyst is preferably chosen from the group formed by the combination of the elements nickel-molybdenum, cobalt-molybdenum and nickel-cobalt-molybdenum and in a very preferred way the active phase is made up of cobalt and molybdenum.

[0067] The catalyst, according to the invention, is prepared according to a process comprising the following steps: a) at least one component of a metal of the VIB group is brought into contact, at least one component of a metal of the group VIII, of the phosphorus with the support, in order to obtain a catalyst precursor; b) if that catalyst precursor from step a) is dried at a temperature below 200 oC, without calcining it later.

[0068] Step a) of contacting the support comprises several modes of use. According to a first way of using step a) of the catalyst preparation process, these components of the metals of the VIB group, group VIII and phosphorus are deposited on this support, by one or more steps of co-impregnations, that is, that these components of the metals of the group VIB, of the group VIII and of the phosphorus are introduced simultaneously in this support. The co-impregnation step (s) is (are) preferably performed by dry impregnation or by impregnation in excess of solution. When this first method comprises the use of several co-impregnation steps, each co-impregnation step is preferably followed by an intermediate drying step generally at a temperature below 2000 oC, advantageously between 50 and 180 oC, preferably between 60 and 150 oC, most preferably between 75 and 140 oC.

[0069] According to a preferred embodiment by co-pregnancy, the aqueous impregnation solution, when it contains cobalt, molybdenum and phosphorus, is prepared under pH conditions favoring the formation of heteropolyanions in solution. For example, the pH of this aqueous solution is between 1 and 5.

[0070] According to a second way of using step a) of the catalyst preparation process, the catalyst precursor is prepared, proceeding with the successive deposits and in an indifferent order of a metal component of the VIB group, a component of a group VIII metal and phosphorus on that support. The deposits can be carried out by dry impregnation, by excess impregnation or by deposit-precipitation, according to methods well known to the Technician. In this second embodiment, the deposit of the metal components of the groups VIB and VIII and phosphorus can be carried out by several impregnations with an intermediate drying step between two successive impregnations, usually at a temperature between 50 and 180 oC preferably between 60 and 150 oC, most preferably between 75 and 140 oC.

[0071] Regardless of the way metals are deposited and the phosphorus used, the solvent that enters the composition of the impregnation solutions is chosen in order to solubilize the metal precursors of the active phase, such as water or an organic solvent (for example , an alcohol).

[0072] As an example, among the sources of molybdenum, oxides and hydroxides, molybdic acids and their salts, in particular ammonium salts, such as ammonium molybdate, can be used phosphomolybdic (H3PMo12O40) and its salts and eventually the molybdic silicic acid (H4SiMo12O40) and its salts. Molybdenum sources can also be hetero polycomposite of the Keggin type, lacunar Keggin, substituted Keggin, Dawson, Anderson, Styrandberg, for example. Molybdenum trioxide and hetero polycompounds of the type Keggin, lacunar Keggin, substituted Keggin and Strandberg are preferably used.

[0073] The tungsten precursors that can be used are also well known to the Technician. For example, tungsten sources include oxides and hydroxides, tungstic acids and their salts, in particular ammonium salts, such as ammonium tungstates, ammonium tungstate, ammonium metatungstate, phosphotungstic acid and its salts, and possibly silicotungstic acid (H4SiW12O40) and its salts. Tungsten sugars can also be heteropolic compounds of the Keggin type, Lacular Keggin, Substituted Keggin, Dawson, for example. Preferably, ammonium oxides and salts, such as ammonium metatungstate or Keggin, lacunar Keggin or substituted Keggin, are used.

[0074] Cobalt precursors that can be used are advantageously chosen from oxides, hydroxides, hydroxy carbonates, carbonates and nitrates, for example. Cobalt hydroxide and cobalt carbonate are used in a preferred manner.

[0075] Nickel precursors that can be used are advantageously chosen from oxides, hydroxides, hydroxy carbonates, carbonates and nitrates, for example. Nickel hydroxide and nickel hydroxy carbonate are used in a preferred manner.

[0076] Phosphorus can advantageously be introduced into the catalyst at different stages of its preparation and in different ways. Phosphorus can be introduced when forming this alumina support, or preferably after forming. It can, for example, be introduced just before or exactly after the peptisation of the chosen matrix, such as, for example, and preferably, the aluminum oxide hydroxide (bohemite) precursor to alumina. It can also be advantageously introduced alone or in admixture with at least one of the metals in the VIB and VIII group. The phosphorus is preferably introduced in a mixture with the precursors of the metals of the group VIB and group VIII, in whole or in part on the formed alumina support, by a dry impregnation of that alumina support as a solution containing the precursors of metals and the precursor of phosphorus. The preferred source of phosphorus is orthophosphoric acid H3PO4, but its salts and esters such as ammonium phosphates or their mixtures are convenient as well. The phosphorus can also be introduced at the same time as the element (s) of the VIB group in the form, for example, of Keggin heteroanions, lacunar Keggin, substituted Keggin or Strandberg type.

[0077] At the end of the step (s) of impregnation of metals in group VIII, in group VIB and in phosphorus, the catalyst precursor is subjected to a drying step b) made by any technique known to the technician. It is advantageously carried out at atmospheric pressure or at reduced pressure. It is advantageously made at atmospheric pressure. This step b) is carried out at a temperature below 200 oC, preferably between 50 and 180 oC, preferably between 60 oC and 150 oC and most preferably between 75 and 140 oC.

[0078] Step b) is advantageously carried out in a crossed layer, using air or any other hot gas. In a preferred way, when drying is carried out in a crossed layer, the gas used is either air or an inert gas such as argon or nitrogen. Most preferably, drying is carried out in a layer crossed in the presence of air.

[0079] Preferably, this drying step lasts between 30 minutes and 4 hours, and preferably between 1 hour and 3 hours.

[0080] At the end of step b) of the process, according to the invention, a dried catalyst is obtained which is not subjected to any subsequent calcination step, for example under the air, at a temperature greater than 200 oC.

[0081] Before being used as a hydrotreating catalyst, it is advantageous to subject the catalyst to a sulfuration step (activation phase). This activation phase is carried out by methods well known in the art, and advantageously under a sulfo-reducing atmosphere in the presence of hydrogen and sulfuric hydrogen. Sulfurized hydrogen can be used directly or generated by a sulfide agent (such as dimethyl disulfide).

[0082] According to another aspect of the invention, the hydrotreating catalyst, as described above, further comprises one or more organic compounds containing oxygen and / or nitrogen. This catalyst is designated by the term "additive catalyst" following the description. The organic compound present in the catalyst contains more than 2 carbon atoms and at least one oxygen and / or nitrogen atom.

[0083] The organic compound containing oxygen can be chosen from a carboxylic acid, an alcohol, an aldehyde or an ester. As an example, the organic compound containing oxygen can be chosen from the group consisting of ethylene glycol, triethylene glycol, glycerol, polyethylene glycol having a molecular weight of 150 to 1500, acetophenone, 2,4-pentane dione , pentanol, acetic acid, maleic acid, oxalic acid, tartaric acid, formic acid, citric acid, a cyclic oligo saccharide composed of at least 6 α-1- linked glycopyranose units, a dialkyl succinate. The dialkyl succinate is preferably a C1-C4 dialkyl succinate, preferably chosen from the group consisting of dimethyl succinate, diethyl succinate, dipropyl succinate and dibuty succinate. Preferably, the C1-C4 dialkyl succinate used is dimethyl succinate or diethyl succinate. Most preferably, C 1 -C 4 dialkyl succinate is dimethyl succinate. According to one embodiment, the organic compound comprises at least the combination of the C1-C4 dialkyl succinate, in particular the dimethyl succinate, and the acetic acid.

[0084] The organic compound that contains nitrogen can be chosen from among an amine. As an example, the organic compound containing nitrogen can be ethylene diamine or tetramethyl urea.

[0085] The organic compound containing oxygen and nitrogen can be chosen from an amino carboxylic acid, an amino alcohol, a nitrile or an amide. As an example, the organic compound containing oxygen and nitrogen can be amino triacetic acid, 1,2-cyclohexa acid in tetraacetic diamine, monoethanol amine, acetonitrile, N-methyl pyrrolidone , dimethyl formamide or ethylene diamine tetraacetic acid (EDTA).

[0086] The catalyst added, according to the invention, is prepared according to a process comprising the following steps: i) at least one component of a metal of the VIB group is brought into contact, at least one component of a metal from group VIII, phosphorus and at least one organic compound containing oxygen and / or nitrogen with the support, in order to obtain an additive catalyst precursor; ii) dry the precursor of the additive catalyst from step i) at a temperature below 200 oC, without subsequently calcining it.

[0087] The molar ratio of organic compound (s) containing oxygen and / or nitrogen per element (s) of the VIB group engaged on the catalyst precursor with additives is comprised between 0.05 to 9 mol / mol, preferably comprised between 0.1 to 8 mol / mol, preferably comprised between 0.2 and 7 mol / mol before drying of step ii).

[0088] For example, when the organic component is a mixture of C1-C4 dialkyl succinate (and, in particular, dimethyl succinate) and acetic acid, these components are advantageously introduced in a corresponding amount: • a a molar ratio of dialkyl succinate (for example, dimethyl) per element (s) of the VIB group of the added catalytic precursor between 0.05 to 2 mol / mol, preferably between 0.1 to 1.8 mol / mol, preferably between 0.15 and 1.5 mol / mol; • a molar ratio of acetic acid per element (s) of the VIB group of the additive catalytic precursor comprised between 0.1 to 5 mol / mol, preferably comprised between 0.5 to 4 mol / mol, preferably comprised between 1.3 and 3 mol / mol and most preferably comprised between 1.5 and 2.5 mol / mol.

[0089] Step i) of putting in contact comprises several modes of use.

[0090] According to a first way of using step i) of the process of preparing the added catalyst, the components of the metals of the group VIB and group VIII, the phosphorus and that of the compound are deposited organic on the support, for at least one co-impregnation step, preferably by dry impregnation. According to this method of use, these components of the metals of the group VIB and group VIII, the phosphorus and the organic compound are introduced simultaneously in this support. This first embodiment of step i) comprises the use of one or more co-impregnation steps, preferably followed by an intermediate drying step generally at a temperature below 200 oC, advantageously between 50 and 180 oC, preferably - range between 60 and 150 oC, most preferably between 75 and 140 oC.

[0091] According to a first way of using step i) of the process of preparing the additive catalyst, at least one organic compound containing oxygen and / or nitrogen is brought into contact with at least one catalytic precursor comprising at least one metal group VIII, at least one metal from group VIB, phosphorus and support. This second method of use is a preparation called "post-impregnation of the organic compound". This is done, for example, by dry impregnation.

[0092] According to this second mode of use, putting in contact according to step i) comprises the following successive steps that will be detailed below: 11) an alumina support is impregnated with at least one solution containing at least at least one group VIB metal, at least one group VII and phosphorus metal to obtain an impregnated support; 12) the impregnated support obtained in step i1) is dried at a temperature below 200 oC without subsequent calcination to obtain a dried catalyst; 13) the dried catalyst obtained in step i2) is impregnated by an impregnation solution comprising at least one organic compound containing oxygen and / or nitrogen to obtain an additive catalyst precursor; 14)) optionally, the additive catalyst precursor obtained in step i3) is allowed to mature.

[0093] In step i1) the introduction of the metals of the VIB group and of the VIII group on the alumina support can be advantageously made by one or more dry impregnations of this aluminum-based support, with the aid of an aqueous solution or organic, containing metal precursors. The precursors of the metal of the VIB group, of the VIII group and of the phosphorus on the alumina support are followed by a drying step i2) during which the solvent (which is generally water) is eliminated, at a temperature less than 200 oC, preferably between 50 and 180 oC, preferably between 60 and 150 oC or between 75 and 140 oC. The drying step of the impregnated support thus obtained is never followed by a calcination step in the air at a temperature greater than or equal to 200 oC.

[0094] It will be noted that steps i1) and i2) correspond respectively to steps a) and b) of the process of preparing the "non-additive" catalyst, according to the invention described above.

[0095] According to step i3), the dried catalyst is impregnated by an impregnation solution comprising at least one organic compound containing oxygen and / or nitrogen. The impregnation solution comprising at least one organic compound is preferably an aqueous solution.

[0096] These organic compound (s) can advantageously be deposited in one or more stages either by over-impregnation, by dry impregnation, or by any other means known to the technician . Preferably, the introduction of the organic compound is carried out by a single impregnation step and particularly preferably by a single dry impregnation step.

[0097] According to step i4) of the preparation process, the catalyst precursor from step i3) can be subjected to a maturation step that is advantageously carried out at atmospheric pressure, at a temperature between 17 oC and 50 oC. The maturation time is usually between 10 minutes and 48 hours and, preferably, between 30 minutes and 5 hours.

[0098] According to step ii) of the preparation process, the catalyst pre-cursor with additives, after possibly a maturation step, is subjected to a drying step at a temperature below 200 oC, without posterior calcination.

[0099] Step ii) drying the process, according to the invention, is advantageously performed by any technique known to the technician. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure.

[00100] This step ii) is advantageously carried out at a temperature between 50 and 180 oC, preferably between 60 oC and 150 oC, and most preferably between 75 oC and 140 oC. Step ii) can be advantageously carried out in a crossed layer, using air or any other hot gas. Preferably, when drying is carried out in a crossed layer, the gas used is either air, or an inert gas with argon or nitrogen. Most preferably, drying is carried out in a layer crossed in the presence of air. Preferably, this step ii) lasts between 30 minutes and 4 hours, and preferably between 1 hour and 3 hours.

[00101] At the end of step ii) of the process, according to the invention, an additive catalyst is obtained that is not subjected to any subsequent calcination step at a temperature greater than or equal to 200 oC.

[00102] According to another alternative embodiment, the process of preparing the additive catalyst combines the co-impregnation of an organic compound and the post-impregnation of an organic compound that can be identical or different from that used for co-impregnation.

[00103] This embodiment comprises the following steps: i) a solution containing at least one component of a metal of the group VIB, at least one component of a metal of the group VIII, phosphorus and mens an organic compound containing oxygen and / or nitrogen with the support, in order to obtain an additive catalyst precursor; i ') the precursor of the additive catalyst from step i) is dried at a temperature below 200 oC, without subsequently calcining it; ii ') the additive and dried catalyst precursor from step i') is contacted with a solution of an organic compound containing oxygen and / or nitrogen; ii) the post-impregnated additive catalyst precursor from step i ") is dried at a temperature below 200 oC, without subsequently calcining it to provide an additive catalyst.

[00104] The operating conditions described above are naturally applicable within the scope of this embodiment.

[00105] Before use, it is advantageous to activate the added catalyst. This activation phase corresponds to a sulfuration that is carried out by methods well known to the technician, and advantageously under a sulfo-reducing atmosphere in the presence of hydrogen and sulfurized hydrogen.

[00106] The additive catalyst obtained is, therefore, advantageously subjected to a sulfuration stage, without intermediate calcination stage. This additive catalyst is advantageously sulfated, either ex situ or in situ. The same sulfurizing agents as those described by the dried catalyst according to the invention can be used.

[00107] The invention also relates to a process of hydrotreating a fraction of hydrocarbons. In particular, the process is a hydrodesulfurization of a fraction of hydrocarbons that has a distillation interval between 30 and 260 oC. Preferably, this fraction of hydrocarbons is a fraction of the gasoline type. Most preferably, the gasoline fraction is a fraction of olefinic gasoline originating, for example, from a catalytic cracking unit (Fluid Catalytic Cracking according to Anglo-Saxon terminology).

[00108] The hydrodesulfurization process, according to the invention, allows the transformation of the organo-sulfur compounds in the hydrocarbon charge into hydrogen sulfide (H2S), limiting as much as possible the hydrogenation of the olefins present in that charge.

[00109] The hydrotreating process consists of putting the hydrocarbon fraction in contact with the catalyst, according to the invention, and hydrogen under the following conditions: • a temperature between 200 and 400 oC, preferably between 230 and 330 oC; • at a total pressure between 1 and 3 MPa, preferably between 1.5 and 2.5 MPa; • an hourly volume velocity (VVH) defined as the volume flow of charge carried to the catalyst volume, between 1 and 10 h-1, preferably between 2 and 6 h-1; • a hydrogen density / gasoline charge between 100 and 600 Nl / l, preferably between 200 and 400 NI / I.

[00110] The catalytic hydrodesulfurization process can be carried out in one or more series reactors of the fixed layer type or of the boiling layer type. If the process is used by means of at least two reactors in series, it is possible to provide a device for removing H2S from the effluent from the first hydrodesulfurization reactor before treating this effluent in the second hydrodesulfurization reactor.

EXAMPLES Example 1 - preparation of a calcined catalyst A (not according to the invention)

[00111] The S1 support of catalyst A is a specific surface transition alumina of 80 m2 / g. This transition alumina is obtained after the following steps: of thermal composition of gibsite at 800 oC (with a short residence time of 0.8 seconds), allowing the obtainment of a transition alumina powder. A wash with water to decrease the sodium content is done on the powder, which is followed by a second rapid dehydration treatment similar to the previous one. The alumina powder thus obtained is then formed in a dredger to form spheres which are then dried at 150 oC. This support finally undergoes a hydrothermal treatment with high partial pressure of water (100%) for 8 hours, then calcined at 850 oC.

[00112] Catalyst A is prepared by dry impregnating the support with an aqueous solution containing molybdenum trioxide, cobalt hydroxide and phosphoric acid. The volume of the solution containing the metal and phosphorus precursors is strictly equal to the volume of water taken up from the support (0.97 ml / g). The concentration of the metal precursors in aqueous solution is adjusted, in order to obtain the desired weight percentage in molybdenum, cobalt and phosphorus on the final catalyst. In order to obtain a complete dissolution of the metal precursors, the impregnation solution is refluxed at 90 oC for 2 hours. After dry impregnation on the substrate, the catalyst is left to mature for 1 h 30 in a water-saturated compartment, dried in an air oven at 90 oC, then calcined under air at 450 oC.

[00113] Catalyst A obtained after calcination has a content of 15.5% by weight in molybdenum (MoO3 equivalent), 3.4% by weight of cork (CoO equivalent) and 3.9% by weight of phosphorus ( equivalent to P2O5), a specific surface of 62 m2 / g and thus a surfacace density in molybdenum of 10.6 atoms per square nanometer of catalyst. This catalyst has atomic Co / Mo ratios of 0.42 and P / Mo of 0.51.

Example 2 - Preparation of a dried catalyst B added in urea and citric acid and containing no phosphorus (not according to the invention).

[00114] The S2 support of catalyst B is a 44 m2 / g specific surface transition alumina obtained by recalcination under air at 1100 oC of an extruded shaped S0 alumina support.

[00115] The S0 support was synthesized by precipitation reaction via a mixture of soda aluminate and aluminum sulfate. This reaction is carried out at a temperature of 60 oC, with a pH of 9, for 60 minutes and under an agitation of 200 rpm. The gel thus obtained is kneaded on a Z-arm kneader to provide a paste. The extrusion is carried out by passing the paste through a die equipped with a 1.6 mm diameter hole in the form of a trilobe. The extruded products thus obtained are dried at 150 oC, then calcined at 450 oC under dry air. The support S0 is then calcined under air at 1100 oC and thus the support S2 is obtained.

[00116] The catalyst is prepared by dry impregnating the S2 support with an aqueous solution containing the precursors of cobalt and molybdenum, respectively cobalt carbonate and ammonium heptamolybdate. This solution also contains urea and citric acid. The concentration of urea and citric acid is determined in order to obtain a urea / molybdate and citric acid / molybdenum molar ratio of 3.8 to 0.6 respectively. The volume of the impregnation solution is adjusted with water, in order to strictly reach the volume of water taken up from the support (0.62 ml / g). The concentration of cobalt and molybdenum in solution is adjusted, in order to obtain the desired weight percentage in molybdenum, cobalt and phosphorus on the final catalyst. After impregnation, the catalyst is dried in an oven under air at 110 oC. No calcination under air is performed thereafter.

[00117] The catalyst B obtained after drying has a content of 15.3% by weight in molybdenum (MoO3 oxide equivalent), 3.3% by weight of cobalt (CoO oxide equivalent), a specific surface of 34 m2 / g, and thus a molybdenum surface density of 18.7 atoms per square nanometer of catalyst (noted with "dMo"). This catalyst has an atomic Co / Mo ratio of 0.41 and does not contain phosphorus.

Example 3- Preparation of the dried catalyst C to I (according to the invention)

[00118] Catalysts C to J are obtained by dry impregnation, according to the same protocol as catalyst A and on different support based on transition alumina, followed by the same maturation and drying steps. No air calcination steps are performed after drying. Aqueous impregnation solutions are obtained by dissolving molybdenum trioxide, cobalt hydroxide and phosphoric acid. The amounts of precursors to be introduced into the solution are adjusted according to the desired weight levels on the final catalyst.

[00119] Aluminas S3, S4 and S5 are prepared by post-treatment of alumina S0 in different conditions. The S3 support is obtained by calcination under moist air at 850 oC (50% water / kg dry air). The S4 support is obtained after hydrothermal treatment at 100 oC in the presence of 6.5% acetic acid for 3 hours in an autoclave, after calcination at 1000 oC under air. The S5 support is obtained by calcination under air of the S4 support at 1150 oC.

[00120] Table 1 gives the characteristics of the supports S1, S2, S3, S4 and S5 used. TABLE 1

[00121] The crystallographic phases are obtained from diffractogram obtained by X-ray diffraction. The specific BET surface is determined by the ni adsorption-desorption method, according to ASTM D3663-03. The median diameter in volume and the total porous volume are obtained by porosimetry to mercury, according to the ASTM D4284-03 standard.

[00122] Table 2 regroups the metal contents of the obtained catalysts, as well as the density (dMo) in metal of the VIB group (the mo- libdene) expressed in number of molybdenum atoms per unit surface of the catalyst (at / nm2 ). TABLE 2

[00123] A representative model charge of a catalytic cracking gasoline (FCC) containing 10% by weight of 2,3-dimethyl but-2-ene and 0.33% by weight of 3-methyl thiophene (ie 1000 ppm by weight of sulfur in the load) is used to assess the catalytic performance of the different catalysts. The solvent used is heptane.

[00124] The hydrodesulfurization reaction (HDS) is operated in a reactor with a fixed layer crossed under a total pressure of 1.5 MPa, at 210 oC, at VVH = 6 h-1 (VVH = charge volume flow / volume me of catalyst) and a volume H2 / load ratio of 300 Nl / l, in the presence of 4 ml of catalyst. Prior to the HDS reaction, the catalyst is sulfurized in situ at 350 oC for 2 hours under a hydrogen flow containing 15 mol% H2S at atmospheric pressure.

[00125] Each of the catalysts is placed successively in this reactor. Samples are collected at different time intervals and are analyzed by gas chromatography in order to observe the disappearance of reagents and the formation of products.

[00126] The catalytic performances of the catalysts are evaluated in terms of catalytic activity and selectivity. The activity in hydrodesulfurization (HDS) is expressed from the speed constant for the HDS reaction of 3-methyl thiophene (kHDS), normalized by the volume of catalyst introduced and assuming an order 1 kinetics in relation to the compound sulfurized. The activity in hydrogenation of olefins (HydO) is expressed from the speed constant of the hydrogenation reaction of 2,3-dimethyl but-2-ene, normalized by the volume of catalyst introduced and assuming a kinetics of order 1 in relation to olefin.

[00127] The selectivity of the catalyst is expressed by the normalized ratio of the kHDS / kHydO velocity constants. The kHDS / kHydO ratio will be so much higher that the catalyst will be more selective.

[00128] The values obtained are normalized, considering catalyst A as a reference (relative HDS activity and relative selectivity equal to 100). The performances are, therefore, the relative HDS activity and the relative selectivity.

[00129] The catalysts, according to the invention, all have an improved selectivity in hydrodesulfurization in relation to the hydrogenation of olefins in relation to catalysts not according to invention A (calcined and B (the catalyst does not contain phosphorus). selectivity of the catalysts is particularly interesting in the case of an application in a gasoline hydrodesulphurisation process containing olefins which seeks to limit octane loss as much as possible due to the olefin hydrogenation.

[00130] Catalysts C to I are also more active in hydro-desulphurisation than non-conforming catalysts A and B.

Example 5 - Preparation of a dried catalyst K1 and K2 (according to the invention) in the presence of an organic molecule in co-impregnation

[00131] The catalysts K1 and K2 are obtained by dry impregnating the support S4. The volume of the aqueous impregnation solution containing the metal and phosphorus precursors is strictly equal to the volume of water taken up from the support (0.91 ml / g). The concentration of the metal precursors in aqueous solution is adjusted, in order to obtain the desired weight percentage in molybdenum, cobalt and phosphorus on the final catalyst.

[00132] Two impregnation solutions were prepared from the solution obtained by dissolving molybdenum trioxide, cobalt hydroxide and phosphoric acid, adding as an organic molecule of citric acid for the first solution and triethylene glycol for the second solution. The first impregnation solution has a citric acid / molybdenum molar ratio of 0.4. The impregnation solutions are brought to reflux at 90 oC for 2 hours, in order to obtain a complete dissolution of the metal precursors in solution. These solutions are then impregnated on the S4 support. After dry impregnation, the catalysts are left to mature for 1h30 in a closed compartment saturated with water, then dried under air in an oven at 120 oC. For the K1 catalyst containing citric acid, the weight levels, in oxide equivalent, in mo- libdene (MoO3), cobalt (CoO) and phosphorus (P2O5) are 10.5, 2.2 and 2, respectively, 9.

[00133] For the catalyst K2 containing triethylene glycol, the weight contents, in oxide equivalent, in molybdenum (MoO3), cobalt (CoO) and phosphorus (P2O5) are 10.4; 2.2 and 2.9. TABLE 4

Example 6 - Preparation of dried catalysts L1, L2 and L3 (according to the invention) in the presence of an organic molecule in post-additive

[00134] The catalysts L1, L2 and L3 are obtained from the dried catalyst E. An additional dry impregnation step is carried out by an aqueous solution, comprising one or more organic molecules in mixture. The volume of the solution is determined from the volume of water taken up from the dried catalyst E (at 0.76 ml / g) and depending on the mass quantity of catalyst to be prepared.

[00135] The L1 additive catalyst precursor is obtained by dry impregnation of an aqueous solution containing citric acid. The concentration of citric acid in solution is determined, in order to obtain a citric acid / molybdenum molar ratio of 0.4.

[00136] The L2 additive catalyst precursor is obtained by dry impregnation of an aqueous solution containing triethylene glycol. The concentration of triethylene glycol in solution is determined in order to obtain a triethylene glycol / molybdenum molar ratio of 0.4. The L3 additive catalyst precursor is obtained by dry impregnation of an aqueous solution, containing dimethyl succinate and acetic acid. The concentration in dimethyl succinate is determined in order to obtain a molar ratio between dimethyl succinate and molybdenum of 0.7 and the volume ratio between acetic acid and dimethyl succinate is fixed at 0.75.

[00137] After dry impregnation, each of the precursors of additive catalysts L1, L2, L3 are left to mature in air at room temperature for 1h30 in a closed compartment in an atmosphere saturated in water, then dried at 140 oC for 2 hours. - ras on the rotary evaporator.

[00138] Before activation, the characteristics of the catalyst precursors L1, L2 and L3 are identical to that of catalyst E.

Example 7 - Evaluation of catalysts K1, K2, L1, L2, L3 compared to catalysts A and B (non-compliant)

[00139] The performances of the catalysts are determined under the conditions of example 4. The results are reported in table 6. TABLE 6

[00140] The catalysts, according to the invention, all have an improved selectivity in hydrodesulfurization in relation to the hydrogenation of olefins in relation to catalysts A (calcined) and B (without calcination and without phosphorus) not according to the invention.

[00141] This improvement in selectivity of the catalysts is particularly interesting in the case of an application in a hydrodesulfurization process for gasoline containing olefins, for which one seeks to limit as much as possible loss of octane due to the hydrogenation of the olefins.

[00142] Furthermore, these catalysts have a much improved relative HDS activity compared to catalysts A (calcined) and B (without calcination and without phosphorus) not complying with the invention. Thus, without this being linked to any theory, the addition of an organic molecule, either in co-impregnation or in post-additive, allows, in addition, to greatly increase the relative HDS activity.

Claims (14)

1. Hydrotreating catalyst, characterized by the fact that it comprises a support consisting of alumina, at least one metal of the group VIB, at least one metal of the group VIII and phosphorus, in which: • the specific surface area of the catalyst it is in the range of 40 to 95 m2 / g; the density of the metal of the VIB group, expressed as the number of metal atoms of the VIB group per unit surface area of catalyst, is in the range of 7 to 30 metal atoms of the VIB group per nm2 of catalyst; the metal density of the VIB group is calculated from the following ratio:

where: o X =% by weight of metal in the VIB group o NA = Avogadro's number, which is equal to 6.022 x 1023; o S = specific surface area of the catalyst (m2 / g), measured according to ASTM D3663; MM = molar mass of the metal in the VIB group; • the content of the metal in the VIB group is in the range of 3% to 35% by weight of oxide of said metal in the VIB group in relation to the total weight of the catalyst; • the content of the group VIII metal is in the range of 0.1% to 10% by weight of the oxide of said group VIII metal in relation to the total weight of the catalyst; • the phosphorus content is in the range of 0.3% to 10% in weight of P2O5 with respect to the total catalyst weight, the catalyst being prepared by impregnating the metals of the group VIB, group VIII and phosphorus in the support, a in order to obtain an impregnated catalyst precur and then drying said impregnated catalyst precur at a temperature below 200 ° C and without subsequent calcination in air at a temperature above 200 ° C and said catalyst is sulfurized after drying. 2. Catalyst according to claim 1, characterized by the fact that the molar ratio of (metal of group VIII) / (metal of group VIB) is in the range of 0.1 to 0.8 and the molar ratio of phosphorus / (metal in the VIB group) is in the range of 0.1 to 0.7. 3. Catalyst according to claim 1 or 2, characterized by the fact that the specific surface area of the catalyst is in the range of 50 to 90 m2 / g. 4. Catalyst according to any one of claims 1 to 3, characterized in that the density of the metal of the VIB group is in the range of 7 to 25 atoms of the metal of the VIB group per nm2 of catalyst, preferably in the range from 7 to 20 metal atoms of the VIB group per nm2 of catalyst, more preferably in the range of 7 to 15 metal atoms of the VIB group per nm2 of catalyst. 5. Catalyst according to any one of claims 1 to 4, characterized by the fact that the metal of the VIB group is selected between tungsten and molybdenum and the metal of the group VIII is selected between nickel and cobalt. 6. Catalyst according to claim 5, characterized by the fact that the metal of the group VIB is molybdenum and the metal of the group VIII is cobalt. 7. Catalyst according to any one of claims 1 to 6, characterized in that the alumina-based support is obtained from an alumina gel that has been beaten, molded and calcined. 8. Catalyst according to any one of claims 1 to 7, characterized by the fact that it comprises at least one organic compound containing oxygen and / or nitrogen, said organic compound being selected from a carboxylic acid lyric, an alcohol, an aldehyde, an ester, an amine, an amino carboxylic acid, an amino alcohol, a nitrile and an amide. 9. Catalyst according to claim 8, characterized by the fact that the organic compound is selected from ethylene glycol, triethylene glycol, glycerol and polyethylene glycol with a molecular weight of 150 to 1500, acetophenone, 2,4-pentanedione, pentanol, acetic acid, maleic acid, oxalic acid, tartaric acid, formic acid, citric acid, a C1-C4 dialkyl succinate, a cyclic oligosaccharide consisting of at least 6 α (1-4) units -linked with glucopyranose, ethylene diamine, tetra-methyl-urea, aminotriacetic acid, 1,2-cyclohexane diamine tetraacetic acid, monoethanolamine, acetonitrile, N-methylpyrrolidone, dimethylformamide and ethylene diamine tetraacetic acid. 10. Process for the preparation of a catalyst as defined in any one of claims 1 to 7, characterized by the fact that it comprises the following steps: (a) depositing the metals of group VIII, group VIB and phosphorus on a support consisting of alumina in one or more impregnation steps, in order to obtain an impregnated catalyst precursor; (b) drying the impregnated precursor at a temperature below 200 ° C, without subsequent calcination in air at a temperature above 200 ° C, in order to provide a dry catalyst; (c) sulfurizing the dry catalyst from step (b). 11. Process for the preparation of a catalyst as defined in claim 8 or 9, characterized by the fact that it comprises the following steps: (i) depositing the metals of group VIII, group VIB, phosphorus and at least one organic compound containing oxygen and / or nitrogen in a support consisting of alumina in one or more impregnation steps, in order to obtain an impregnated catalyst precursor; (ii) drying the impregnated precursor at a temperature below 200 ° C without subsequent calcination to air at a temperature above 200 ° C, in order to provide a dry catalyst, (iii) sulfurizing the dry catalyst from step (ii ). 12. Process according to claim 11, characterized by the fact that step (i) comprises the following successive steps: (11) impregnating an alumina support with at least one solution containing at least one metal in the group VIB, at least one group VIII metal and phosphorus, in order to obtain an impregnated support; (12) drying the impregnated support obtained in step (i1) at a temperature below 200 ° C without subsequent calcination in air, in order to obtain a dry catalyst; (13) impregnating the dry catalyst obtained in step (i2) with an impregnation solution comprising at least one organic compound containing oxygen and / or nitrogen to obtain a coated catalyst precursor; (14) optionally, allowing the precursor of the coated catalyst obtained in step (i3) to mature. 13. Process for the hydrodesulfurization of a gasoline cut, characterized by the fact that the said cut of gasoline, hydrogen and a catalyst, as defined in any one of claims 1 to 9, are brought into contact, being the referred sulfurized catalyst and the contact being made at: • a temperature in the range of 200 ° C to 400 ° C; • a total pressure in the range of 1 to 3 MPa; • an hourly spatial speed, defined as the volumetric flow of the feed in relation to the volume of the catalyst, in the range of 1 to 10 h-1; • a hydrogen / gas supply volume ratio in the range of 100 to 600 NL / L. 14. Process according to claim 13, characterized by the fact that gasoline is gasoline obtained from a catalytic cracking unit.